Supervisory control system



Nov. 3, 1936. I J. OLIVER 2,059,896

SUPERVISOR! CONTROL SYSTEM Filed July 8, 1932 2 Sheets-Sheet l l I l I lI l T N \l Invencon; James H OLiver,

His Attorney.

Nov. 3, 1936. J. H. OLIVER 2,059,896

SUPERVISORY CONTROL SYSTEM Filed July 8, 1932 2 Sheefcs-Sheet 2Inventor: James HOLiver;

by MM His Attorney.

Patented Nov. 3, 1936 UNITED STATES PATENT OFFICE James H. Oliver,Aldan, Pa., assignor to General Electric Company, a corporation of NewYork Application July 8, 1932, Serial No. 621,405

20 Claims.

My invention relates to supervisory control systems for supervising andcontrolling apparatus in a remote station from a control station, suchas a dispatchers office, and particularly to an improvement in thesynchronous selector supervisory control system disclosed and claimed inthe copending application, Serial No. 260,168, filed March 8, 1928, byClyde E. Stewart, and assigned to the assignee of this application.

One object of my invention is to provide an improved arrangement ofapparatus whereby the synchronous selector supervisory control systemdisclosed in the aforesaid copending appli cation may be employed tosupervise and control a large number of apparatus units over a singlepair of line conductors between the dispatchers ollice and the remotestation in which the apparatus units to be supervised and controlled arelocated. As disclosed in the aforesaid copending application four lineconductors are required between the dispatchers office and the remotestation.

In accordance with my invention, there is provided at the dispatchersoffice a group of control keys and signalling devices, such as lamps,for each apparatus unit to be supervised and controlled in the remotestation. Suitable selecting means are provided at the dispatchers officefor successively associating in a predetermined sequence these groups ofcontrol keys and lamps with the single pair of line conductors extendingbetween the dispatchers office and the remote station. Similar selectingmeans are provided at the remote station for successively associating inthe same sequence the corresponding apparatus units with the single pairof line conductors. In order that each of the control keys and lamps inthe dispatchers oflice may be associated with the two line conductors atthe same time that the corresponding apparatus unit in the remotestation is associated with the two line conductors, suitable means areprovided for transmitting impulses over the line conductors in series toeffect the synchronous operation of the two selecting means. Inaccordance with the preferred embodiment of my invention, thissynchronous operation of the two selecting means is effected by thealternate transmission of impulses of opposite polarity through the twoline conductors in series.

Normally the two selecting means in the two stations are not inoperation. At the dispatchers office there is a common start key which,when operated by the dispatcher, starts the two select- I ing means intooperation to associate each apparratus unit and its corresponding groupof control keys and lamps simultaneously with the two line conductors.The operation of the two selecting means is also arranged to be startedin response to an automatic operation of any one of the apparatus unitswhile the selecting means are in their respective normal positions.

Whenever a group of control keys and lamps is associated with itscorresponding apparatus unit by the selecting means, there istransmitted through the two line. conductors a signalling current whichcorresponds in character to the position of the apparatus unit, Thissignalling current controls the group of signalling lamps at thedispatchers oflice so that it indicates the actual position of thecorresponding apparatus unit. Each group of lamps is also arranged toindicate any change that occurs in the position of the correspondingapparatus unit. In accordance with the preferred embodiment of myinvention, an alternating current of one frequency is transmittedthrough the two line conductors in series to the dispatchers ofiice whenan apparatus unit, which is associated with the two line conductors, isin one position and an alternating current of a dilierent frequency istransmitted when the apparatus unit is in a different posi tion.Suitable frequency responsive means are provided at the dispatchersoffice for selectively operating the corresponding group of lamps inaccordance with the frequency of the signalling current transmitted.

In order that a dispatcher may effect a change in the position of anapparatus unit at the remote station, each group of control keys at thedispatchers ofiice includes a select key which, when operated by thedispatcher prior to his operation of the start key, causes the twoselecting means to stop operating when the group of control keys andlamps associated with the operated select key and the correspondingapparatus unit are simultaneously associated with the two lineconductors. A check lamp associated with the operated select key lights,when the selecting means stop in the desired positions, and indicates tothe dispatcher that the desired apparatus unit has been selected by theselecting means. The dispatcher then operates a common operate key toefiect the operation of the selected apparatus unit. The operation ofthis operate key causes operating current toflow, through the two lineconductors in series, to the remote station where suitable means are provided which operate in response to this operating current to eiiect thedesired operation of the selected apparatus unit. As soon as theselected apparatus unit changes its position, the character of thesignalling current transmitted over the two line conductors to thedispatchers station is also changed to effect the proper change in thelighting of the corresponding indicating lamps. By successivelyoperating the operate key, the dispatcher can operate the selectedapparatus unit as many times as he desires.

After the dispatcher has effected the desired operation of the selectedapparatus unit, he restores the corresponding select key to its normalposition. This starts the two selecting means into operation again andif no other select key is in its operated position, the selecting meansreturn to their respective normal positions where they stop until eitherthe start key is again op erated or an apparatus unit automaticallychanges its position. When the selecting means reach their normalpositions, the start lamp is lighted and a suitable alarm, such as abell or horn, is operated at the dispatchers office. The lighting of thestart lamp informs the dispatcher that the selecting means are in theirrespective normal positions and that the supervisory system is in anoperative condition and the operation of the alarm informs thedispatcher that the operation of the selecting means has been completed.

When the operation of the selecting means is effected in response to anautomatic operation of an apparatus unit, the selecting means operate inthe same manner as when the operation thereof is effected by theoperation of the start key in the dispatchers office except that as soonas the selecting means start to operate, an alarm is operated to informthe dispatcher that an apparatus unit has been automatically operated inthe remote station. During the operation of the selecting means, thegroup of lamps associated with the apparatus unit which has changed itsposition is operated in a manner to indicate to the dispatcher whichparticular apparatus unit has been operated.

My invention will be better understood from the following descriptionwhen taken in connection with the accompanying drawings and its scopewill be pointed out in the appended claims.

Referring to the accompanying drawings, Figs. 1 and 2 when takentogether diagrammatically illustrate a supervisory control systemembodying a preferred embodiment of my invention, the apparatus andcircuits at the dispatchers office being shown diagrammatically in Fig.1 and the apparatus and circuits at the remote station beingdiagrammatically shown in Fig. 2.

General description of the system In the arrangement shown in thedrawings two line conductors LI and L2 extend between the dispatchersofiice and the remote station. At the remote station a selector switch Ais provided for successively associating the apparatus units thereatwith the two line conductors L| and L2 in a predetermined sequence. Atthe dispatchers office a similar selector switch A is provided forsuccessively associating the corresponding groups of control keys andindicating lamps with the two line conductors LI, L2 in the samesequence. Preferably each selector switch is of the well known typewhich comprises a plurality of banks of contacts, each of which hasassociated therewith a cooperating wiper, and a suitable motor magnetfor simultaneously moving all of the wipers in a step by step mannerover the contacts in the respective banks. Any other suitable selectingmeans examples of which are well known in the art may be used however.As shown in the drawings the switch A consists of five banks of contactsC, S, I, T and N, a cooperating wiper for each bank and an operatingmagnet m for the five wipers; and the switch A consists of six banks ofcontacts Cl, C, S, I, T and N, a cooperating wiper for each bank and anoperating magnet m for the six wipers. Each bank contains 25 contacts sothat each switch has 25 different positions. Normally each switch is inits zero or normal position, as shown. Each of the other positions,except the last, is allotted to a different apparatus unit so that withthe arrangement shown twenty-three different apparatus units can besupervised. In order to simplify the disclosure, however, only theindividual control devices and circuits for the apparatus units AU-lwhich is allotted to the first position of each switch and for theapparatus unit AU-23 which is allotted to the twenty-third position ofeach switch, are shown. It will be evident, however, that similarapparatus unit may be allotted to each of the other twenty-one positionsbetween the first and twenty-third positions of the switches.

As shown in the drawings, the apparatus units AU| and AU-23 are circuitbreakers of the well known latched-in type but it is obvious that eachapparatus unit may be any other suitable control device. Each apparatusunit is provided with a suitable closing coil, such as CC-! forapparatus unit AUI and CC--23 for the apparatus unit AU -23, and with asuitable trip coil, such as TC-l for the apparatus unit AU! and TC-23for the apparatus unit AU23. Associated with each apparatus unit is acontrol relay, such as CRi and CP.,23 for the apparatus units AU--| andAU-23 respectively, which selectively controls the energization of theclosing and trip coils of the associate apparatus unit. As shown, thesecontrol relays are polarized relays of the well known type whosearmature returns to the neutral position when deenergized after eachoperation. Each control relay has its respective winding connectedbetween the contact in bank C which is allotted to the associateapparatus unit and the neutral terminal 11. of a battery BAT which isprovided at the remote station. Therefore, with this arrangement it willbe seen that when the wiper associated with the bank C is in engagementwith a contact which is allotted to an apparatus unit. the direction ofcurrent flow through the wiper and contact of bank C determines whetherthe associate control relay completes the closing coil circuit or thetrip coil circuit of the associate apparatus unit.

As shown, the circuit of each trip coil is also arranged to be completedby an overload relay such as OL! and OL23 for the units AUi and AU-23respectively which is so connected as to be responsive to an abnormalcurrent through the associate circuit breaker.

At the dispatchers office the group of control relays and indicatinglamps corresponding to the apparatus unit AU| consists of a two positionselect key SK-l which is operated when it is desired to have theselector switches A and A stopped with their wipers in engagement withthe first contacts in the respective banks, a two position control keyCK| which controls the operation of the indicating lamps, a red lamp R-lwhich, when energized, indicates that the apparatus unit AUl is in itsclosed position, a green lamp G-| which when lighted indicates that theapparatus unit AU-| is in its open position, a white lamp W-l which whenlighted indicates that the position of the apparatus unit AU--I does notcorrespond with the position of the control key CK| and an amber lightAM-| which when lighted indicates that the switches A and A have stoppedwith their wipers in engagement with the contacts allotted to theapparatus unit AU-I. The group of control keys and lamps correspondingto the apparatus unit AU-23 similarly consists of a select key SK23, acontrol key CK-23, a red lamp R23, a green lamp (i-23, a white lamp W-23and an amber lamp AM23.

Each group of control keys and indicating lamps has associated therewithan individual indicating relay, such as IR! and IR-23 for the lampscorresponding to the apparatus units AU-I and AU23 respectively, whichdetermines by its position whether the associate red or green lamp islighted. Each indicating relay also determines in conjunction with theassociate control key whether the associate white lamp is lighted. Asshown in Fig. l, the relays IR-| and IR23 are in positions to effect thelighting of the lamps R-l and R-23 respectively since the correspondingapparatus units AUI and AU23 are shown in their closed positions. Sincethe control keys CK| and CK-23 are also shown in their closed positionsthe positions of these keys agree with the positions of thecorresponding apparatus units and, therefore, the white lamps Wl and WZ3are not. lighted. It will be seen, however, that if either of thecontrol keys were in its other position, the associate white lamp wouldbe lighted.

Each indicating relay is shown as a polarized relay of the well knowntype whose armature remains in the last position to which it isoperated. The operating coil of each indicating relay is connectedbetween the neutral terminal 11 of a battery BAT at the dispatchers oifice and the bank I contact allotted tothe corresponding apparatusunit. For example, the operating coil of the relay IP,-I is connectedbetween the bat tery terminal n and the first contact in bank I, and theoperating coil of relay IR23 is connected between the battery terminal nand the twenty-third contact in bank I. The direction of the currentthrough the operating coil of each indicating relay is determined by theposition of the corresponding apparatus unit in a manner which will behereinafter described.

In order that each group of control keys and indicating lamps may beassociated with the two line conductors L-! and L2 at the same time thecorresponding apparatus unit is associated therewith, it is essentialthat the wipers of the two switches shall engage their correspondingcontacts at the same time. This result is ob tained by completing asynchronizing circuit through the two line conductors when both switchesoccupy corresponding positions and providing means which responds to thecurrent flowing through the synchronizing circuit for effecting thesimultaneous operation of the motor magnets of the two switches. In thearrangement shown, the line conductor L2 is normally connected to themid or neutral terminals n and n of the batteries BAT and BATrespectively. The line conductor L! is normally connected to the wipersof the banks S and S respectively.

In the dispatchers oflice the adjacent contacts of the bank S areconnected to the opposite polarity terminals of the battery BAT throughthe normally closed contacts of the corresponding select keys. Forexample, the first and twentythird contacts of the bank S arerespectively connected to the positive terminal of the battery BATthrough the normally closed contacts of the select key SKl and SK23. Atthe remote station the adjacent contacts of the bank S are connected tothe opposite polarity terminals of the battery BAT. The correspondingcontacts of the two banks S and S, however, are connected to oppositepolarity terminals of the respective batteries. For example, the firstcontact of the bank S is connected to the positive terminal of thebattery BAT, and the first contact of the bank S is connected to' thenegative terminal of the battery BAT. Therefore, as the wipers of thetwo switches A and A simultaneously engage successive contacts in theirrespective banks, current impulses of opposite polarity flow through thetwo line conductors Ll and L2 in series. At the dispatchers ofiice thesecurrent impulses of opposite polarity cause a two-position polarizedrelay SSR, the operating winding of which is connected in series withthe line L-l, alternately to reverse the position of its armature. Inthe remote station the current impulses of opposite polarity cause asimilar two-position polarized relay SSR', the operating winding ofwhich is connected in series with the conductor Ll, alternately toreverse the position of its armature. The alternate operation of thearmatures of the two relays SSR and SSR effects the energization of themotor magnets m and m, the circuits of which are respectively completedthrough the contacts of the banks N and N of the selectors A and A.

When the selector switches A and A are in their normal positions, asshown in the drawings, the line conductor L--l is connected to thepositive terminal of the battery BAT at the remote station, through theoperating winding of the relay SSR, wiper and normal contact of the bankS and winding of a start relay E; and to the negative terminal of thebattery BAT at the dispatchers ofiice, through the operating winding ofthe relay SSR, the wiper and normal contact of the bank S and thewindings of the line check relays SI and E. The current in this normallycompleted circuit is neither sufiicient to cause the start relay E toclose its contacts nor to cause the line check relay E to open itscontacts. The current, however, is suflicient to cause the line checkrelay 8-4 to close its contacts and complete an energizing circuit forthe starting indicating relay H.

The starting indicating relay H, when energized, completes a circuit fora start light STL at the dispatchers oflice which, when lighted, informsthe dispatcher that the selector switches are in their respective normalpositions and that the line conductors are neither open norshort-circuited. If the line wires were open circuited, the circuitthrough the relay S! would be open and, therefore, the circuit of therelay H would be open at the contacts of the relay S-l and the startlight STL would not be lighted. If the two line conductors wereshort-circuited, the relay E would be energized sufficiently to open itscontacts in the energizing circuit of the relay H so that the startlight S'I'L would not be lighted.

In order that the dispatcher may start the two selector switches A and Aoperating when they are in their normal positions, there is provided atthe dispatchers ofiice a start key STK which, when operated, completesan energizing circuit for a start relay P through the wiper and normalcontact of the bank T. The start relay P, when energized, completes alow resistance shunt circuit around the windings of the relays Sl and Eso that the current fiowing through the line conductor L-I is increasedsufiiciently to cause the relay E at the remote station to close itscontacts. An energizing circuit is then completed for an auxiliary startrelay F which, in turn, completes a locking circuit for its operatingcoil and also a shunt circuit around the winding of the start relay E.When the windings of the three relays S-l, E and E are allshort-circuited, sufiicient current flows through the windings of therelays SSR and SSH. to cause their respective armatures to move to theirother position and thereby eiiect the operation of the motor magnets mand m to move the switches A and A to their first positions. Thesynchronous operation of the selector switches then continues untileither the selector switches return to their normal positions or acontact in bank S is reached whose associated select key has beenoperated by the dispatcher. As soon as the wiper associated with thebank S engages such a contact, the selector switches stop since thesynchronizing circuit is then open at this point. Therefore, it will beseen that the dispatcher can cause the selector switches to move fromtheir normal position to any desired position merely by first operatingthe select key associated with the desired position and then operatingthe start key STK.

When the selector switches A and A stop with their wipers on thecontacts corresponding to an operated select key, a circuit is completedat the dispatchers ofice for the amber light associated with theoperated select key. This amber light circuit is completed through theindividual contact of bank T corresponding to the selected apparatusunit and contacts of a position check relay B which are closed onlyafter the selector switches have established the proper connections. Theoperation of the relay B is controlled by a time relay pick-up relay Dwhich is connected so that, when in its deenergized position, itcompletes an energizing circuit for a time delay dropout relay C. Thewinding of the relay D is connected so that, when the selector switch Ais in operation, the relay is in its deenergized position and the relayC is energized, but after the selector switch A has remained in any ofits positions for a predetermined time, the relay D operates andinterrupts the energizing circuit of the relay C. The relay C, whenenergized, closes contacts in the energizing circuit of the relay B.This energizing circuit of the relay B also includes contacts of therelay Al which is alternately connected between the wiper associatedwith bank S and the positive and negative terminals of the battery BATby the operation of the relay SSR. Whenever the select key in serieswith a contact of the bank S is closed, the relay AI is short-circuitedwhen the cooperating wiper associated with the bank S engages such acontact. When, however, the wiper stops in engagement with such acontact whose associate select key has been opened by the dispatcher,the relay Al is sufficiently energized to complete an energizing circuitfor the relay B before the time relay C operates to open its contacts inthe energizing circuit of the relay B. The relay B in addition tocompleting the circuit of the amber light associated with the operatedselect key also completes a locking circuit for its operating coil sothat the relay B is not deenergized by the relay C when it opens itscontacts in the energizing circuit of the relay B after the selectorswitch A has been stopped for a predetermined time.

After the selector switches A and A have established the properconnections to the desired apparatus unit, the dispatcher can operateselected apparatus unit by operating a common operate key OK. Theoperation of this key OK completes an energizing circuit through thecontacts of check relay B for an operate relay F which, when energized,disconnects the relay SSR and the wiper associated with bank S from theline conductor Ll and the neutral terminal in of battery BAT from theline conductors L2 and connects the line conductors Ll and L-2 to thewipers of banks C and Cl respectively. In each of the banks C and C| theadjacent contacts are connected to opposite polarity terminals of thebattery BAT but corresponding contacts of the two banks are alsoconnected to opposite polarity terminals. For example the first, thirdetc. contacts of bank C and the second, fourth etc. contacts of bank Clare connected to the negative terminal of battery BAT whereas the first,third etc. contacts of bank CI and the second, fourth etc. contacts ofbank C are connected to the positive terminal of the battery BAT.Therefore, the direction of the operating current which flows throughthe two line conductors when the relay F is energized depends upon theposition of the switch A. The operating current also is always in thesame direction as the last synchronizing current impulse. For example inthe arrangement shown the synchronizing current impulse which causes theswitches to move from their zero to their first position flows from theremote station through the conductor L-l to the dispatchers ofiice andback to the remote station through line conductor L2. When the switchesare in their first position the operating current flows from the remotestation through line conductor Irl to the dispatchers ofiice and back tothe remote station through line conductor L 2.

Therefore this operating current is in a direction to maintain thearmature of the synchronizing relay SSR. in the remote station in theposition to which it was last operated in response to the lastsynchronizing current impulse. The direction of this operating current,however, is such as to operate a polarized master operate relay MOR' inthe remote station so that it closes its contacts. This relay MOR' hastwo operating windings 2 and 3 which are respectively connected toalternate contacts of bank S and which are arranged so that thesynchronizing current which flows through them in the difierentpositions of the switch A causes the relay MOR to maintain its contacts15 open. When however a reverse control current flows through either ofthese two windings the relay MOB closes its contacts l5 and completes acircuit for either the auxiliary control relay M or the auxiliarycontrol relay K depending upon the position of the selected apparatusunit. If the selected apparatus unit is closed, a circuit is completedthrough the corresponding contact of bank I and auxiliary contacts onthe selected apparatus unit for a master indicating relay MIR which isof the polarized type, so that current flows through the apparatus unit.

operating winding of the relay MIR in the proper direction to cause itto close an energizing circuit for the auxiliary control relay M. If theselected apparatus unit is open, the circuit of the master indicatingrelay MIR is completed in such a manner that current flows through itsoperating winding in the opposite direction and' the relay closes anenergizing circuit for the auxiliary control relay K". Therefore, whenthe master operate relay MOR" closes its contacts, a circuit forauxiliary control relay M" is completed through contacts of the masterindication relay MIR if the selected apparatus unit is closed and acircuit is completed for the auxiliary control relay K if the selectedapparatus unit is open. The auxiliary control relay M, when energized,completes a circuit for the operating coil of the control relayassociated with the selected apparatus unit through its correspondingcontact of the bank C so that current flows through the control relay inthe proper direction to cause the relay to complete an energizingcircuit for the trip coil of the selected apparatus unit. When theauxiliary control relay K is energized, a similar circuit is completedfor the operating coil of the control relay associated with the selectedapparatus units except that the current flows in the opposite directionthrough the operating coil so that the control relay effects theenergization of the closing coil of the selected apparatus unit.Therefore, by successively closing the operate key OK, a selectedapparatus unit can be successively opened and closed as many times asthe dispatcher desires.

In order to prevent the control circuit of an apparatus unit from beingcompleted during the operation of the selector A, a control cut-oilrelay B is provided at the remote station. This relay B controls thecircuits of the relays K and M so that they are maintained open untilafter the synchronizing relay SSR has remained stationary in one of itstwo positions for a predetermined time.

In order to effect the operation of each group of signal lamps at. thedispatchers oflice in accordance with the position of the correspondingapparatus unit in the remote station during each operation of theselector switches A and A, two

' suitable sources of alternating current of different frequencies AC-|and AC -2 are provided at the remote station and means are provided ineach position of the selector switch A allotted to an apparatus unit forselectively connecting the sources of current across the two lineconductors Ll and L2 in accordance with the position of thecorresponding apparatus unit. In the arrangement shown in the drawings,the source of current AC'--i is arranged to be connected across the lineconductors Ll and L-2 when the selected apparatus unit is in oneposition and the source AC2 is arranged to be connected across the lineconductors when the apparatus unit is in its other position.

The connection of the sources AC-l and AC'2 across the line conductorsis controlled by an auxiliary master indication relay P of the polarizedtype. The operating winding of the relay P is connected in parallel withthe operating winding of the master indication relay MIR.

In each position of the switch A, allotted to an apparatus unit, thewinding of the relay P is connected by the wiper associated with thebank I to auxiliary contacts on the corresponding If the apparatus unitis closed,

current flows in a direction through the operaing winding of the relay Pto cause the relay to effect the connection of the source AC-l acrossthe line conductors L| and L2, whereas if the apparatus unit is opencurrent flows in the 0pposite' direction through the operating windingof the relay P so that the relay effects the connection of the sourceAC2 across the line conductors. Therefore, as long as the switch A is ina position allotted to an apparatus unit, signalling currentcorresponding in character to the position of the apparatus unit, istransmitted over the line conductors in series to the dis patchersoffice. a

. At the dispatchers oflice suitable frequency responsive means isprovided for controlling the groups of signal lamps in response to thefrequency of the signalling current transmitted thereto from the remotestation. As shown, this frequency responsive means is a masterindication relay MIR, of the balanced relay type, which has two opposingwindings ACI and AC2 normally connected in parallel across the lineconductors L--I and L-2. The circuit of the winding AC-I isv designed sothat it is tuned to the frequency of the source AC-l and the circuit ofthe winding AC2 is designed so that it is tuned to the frequency of thesource AC2. The master indication relay MIR selectively controls thepolarity connected to the wiper associated with bank I so that as thecircuits of the indication relays are successively completed by thewiper, current flows through each indication relay in the properdirection to cause it to efiect the lighting of the associate group ofsignal lamps in accordance with the position of the correspondingapparatus unit. For example, if the apparatus unit is closed when theselector switches A and A are in the position allotted to that apparatusunit, the source AC! is connected across the line conductors and thecurrent in the winding ACI of the master indication relay MIR is greaterthan the current in the winding AC-2. Consequently, the relay MIRconnects the positive terminal of the battery BAT to the wiperassociated with bank I so that current flows through the operatingwinding of the indication relay in the proper direction to efiect thelighting of its associate red lamp. If, however, the apparatus unit isin its open position, the source AC2 is connected across the conductorsinstead of the source AC-l and, therefore, the relay MIR connects thewiper associated with the bank I to the negative terminal of the batteryBAT instead of to the positive terminal. Consequently, the indicationrelay corresponding to the apparatus unit is operated so as to effectthe lighting of its associate green lamp.

In order that the master indication relay MIR may have sufiicient timeto change its position before the circuit through the wiper associatedwith the bank I is completed thereby when the switch A moves from oneposition to the next, the circuit through the wiper associated with thebank I also includes the contacts of a relay X. The winding of the relayX is alternately connected to the positive and negative terminalsof thebattery BAT by the synchronizing relay SSR, The relay X is designed sothat it opens its contacts each time the selector switch Ais moved fromone position to the next. In this way the circuit through the wiper ofthe bank I is maintained open for a sufficient length of time after theselector switch reaches its new position to allow the master indicationrelay MIR to assume a position corresponding to the position of theapparatus unit allotted to the new position of the selector switchbefore the circuit through the bank I is completed.

In order to efiect the automatic operation of the selector switches Aand A from their normal position when an apparatus unit in the remotestation automatically changes its position, each apparatus unit hasassociated therewith an indication auxiliary relay such as IAI and IA23for the apparatus units AU-l and AU23 respectively. The circuit of eachindication auxiliary relay is normally completed through auxiliarycontacts on the associate apparatus unit so that when the apparatus unitchanges its position, the corresponding indication auxiliary relaybecomes deenergized. If the selector switch A is in its normal positionso that the zero position relay H is energized, the deenergization ofany indication auxiliary relay completes a circuit for a-start relay D.The relay D then completes through the wiper and zero contact of thebank I a circuit for the operating winding of the auxiliary masterindication relay P so that current flows through this operating windingin the proper direction to efiect the connection of the alternatingcurrent source ACI across the line conductors L-l and L2. Thisalternating current causes the master indication relay MIR- at thedispatchers ofiice to operate and complete through the wiper and normalcontact of the bank I and a normal contact of the start key STK anenergizing circuit for the start relay P. The start relay P then effectsthe starting of the selector switches A and A in the same manner as whenit is energized in response to the closing of the start key STK. Theselector switches then continue to operate until they reach their normalposition. As the wipers of the bank I and I pass over their respectivecontacts, signal currents corresponding in character to the positions ofthe associate apparatus units are transmitted over the line conductors.The position of each indication relay in the dispatchers office is,therefore, checked and if it does not agree with the correspondingapparatus unit, it is operated to the position corresponding thereto. Inthe group of lamps associated with the automatically operated apparatusunit in the remote station, the white lamp is lighted to show thedispatcher which apparatus unit has changed its position.

As soon as the selector switch A reaches the position allotted to theapparatus unit which has changed its position, an energizing circuit iscompleted for the associate deenergized indication auxiliary relaythrough the wiper and corresponding contact in bank T. The indicationauxiliary relay then completes a locking circuit for its operating coilwhich is independent of the corresponding contact in the bank T.

In order to prevent the alternating current circuit which is used assignalling current from operating any of the direct current devices,suitable retardation coils RCI and RC-l are respectively connected inseries with the line conductor LI at the dispatchers ofiice and at theremote station and similar retardation coils RC2 and RC-2 arerespectively connected in series with the line conductor L2 at thedispatchers office and at the remote station. The source ACl and AC--2and the windings ACi and AC2 are connected to the line conductor L-l atpoints intermediate the retardation coils RC-l and RC'-[ and to the lineconductor L--2 at points intermediate the retardation coils R.C2 andRC2.

In order to prevent the direct current impulses from flowing through thesources AC-| and AC2 and the windings AC-l and AC2, a suitable condenserCONi is provided in the connection between the sources AC--l and AC--2and the line conductors Ir-l, a suitable condenser CON2 is provided inthe connection between the sources ACI and AC2 and the line conductorL2, and suitable condensers CONl and CON2 are respectively connected inseries with the windings ACI and AC-2 of the master indication relayMIR.

At the dispatchers ofiice there is provided a suitable alarm AL such asan electric horn. The circuit of this alarm is controlled by an alarmrelay K the circuit of Which is controlled by the starting indicationrelay H so that each time the relay H changes its position, the circuitof the alarm relay is opened to efiect the operation of the alarm AL.Since the relay H is energized each time the switches A and A move totheir normal position and is deenergized each time the switches A and Aleave their normal position, the relay K is deenergized to effect theoperation of the alarm each time the selector switches leave theirnormal position in response to an automatic operation of an apparatusunit and each time the switches A and A return to their normal position.In order to prevent the alarm from being operated when the selectorswitches A and A start in response to the operation of the start keySTK, the circuit of the alarm includes normally closed contacts on thestart key STK. A suitable alarm key AK is provided for controlling thecircuit of the relay K so that either a short or a continuous operationof the alarm may be effected in response to the deenergization of therelay K.

At the dispatchers oflice there is also provided an emergency reset keyERK which is operated by the dispatcher to efiect the resetting of theselector switches to their normal position if for any reason they do notreturn automatically.

At the remote station a battery potential relay A'l whose operating coilis connected di rectly across the terminals of the battery BAT, isprovided for completely disconnecting the line conductors Ll and L-2from the battery BAT in case the potential thereof decreases below apredetermined value.

Detail description of the operation of the system The operation of thearrangement shown in the drawings is as follows: When the apparatusunits AU-l and AU23 are closed and the selector switches A and A are intheir normal position, the various control devices occupy the positionsin which they are shown in the drawings. At the dispatchers oifice thered lamps R--| and R3 are lighted, the circuits of these lamps beingrespectively completed through the left-hand contacts of the indicationrelays IP,I and IR23. The contacts 5 of the synchronizing relay SSRcomplete energizing circuits for the relay X and the relay D between theneutral terminal 11 and the positive terminal of the battery BAT.

At the remote station the wiper and normal contact of the bank Tcompletes an energizing circuit for the zero position check relay Hbetween the positive terminal and the neutral terminal n of the batteryBAT. The contacts 6 of the synchronizing relay SSR complete anenergizing circuit for the line cut-off relay C between the negativeterminal and the neutral terminal n of the battery BAT. The relay C, inturn, completes through its contacts 1 and the contacts 6 of the relaySSR an energizing circuit for the control cut-01f relay B between thenegative terminal and the neutral terminal n of the battery BAT. Theindication auxiliary relay IA-l is energized by a circuit which iscompleted between the negative terminal and the neutral terminal 11 ofthe battery BAT by the auxiliary contacts 8 on the apparatus unit AU-land the contacts 9 of the relay IA--l. A similar circuit is completedfor the indication auxiliary relay IA23 through the auxiliary contactsIn on the apparatus unit AU-23 and the contacts ll of the relay IA23.

Also when the selector switches are in their normal position, a checkcircuit is completed to effect the lighting of the start lamp STL if thesupervisory system is in an operative condition and to efiect theoperation of the alarm AL if the line conductors L--I and L2 are eitheropen or short-circuited or if the potential of the battery BAT at theremote station is below a predetermined value. This check circuit isfrom the positive terminal of the battery BAT through the winding ofrelay E, wiper and normal contact of bank S, contacts l2 of relay C,winding of relay SSR', retardation coil RCI, contacts I3 of relay A'|,line conductor Ll, retardation coil RCI, contacts I 4 of relay F,winding of relay SSR, wiper and normal contact of bank S, contacts l5 ofrelay D, winding of relay Sl, winding of relay E, contact E6 of key ERK,negative terminal of battery BAT, neutral terminal n of battery BAT,contacts I! of relay F, contacts N3 of relay P, retardation coil RC-Z,line conductor LZ, contacts IQ of relay AI, retardation coil RC2 to theneutral terminal 11. of battery BAT. Also from the normal contact ofbank S a parallel circuit is completed to the negative terminal ofbattery BAT through contacts 4| of relay B and resistor 42 in parallelwinding of relay A--l, and contacts 93 of relay SSR.

Th normal current in this check circuit is sufficient to cause the relayS-l to close its contacts 19 but is not sufiicient to operate any of theother relays whose windings are connected in this check circuit. Therelay Sl by closing its contacts l9 completes an energizing circuit forthe check relay H. This circuit which also includes the contacts 26 ofthe relay E is connected between the negative terminal and the neutralterminal n of the battery BAT. When the relay H is energized, itscontacts 2! complete a circuit for the start lamp STL which, whenlighted, informs the dispatcher that the supervisory system is in anoperative condition. At its contacts 22 the relay H maintains a lockingcircuit for the alarm relay K completed between the positive terminaland the neutral terminal n of the battery BAT. This locking circuit forthe alarm relay K also includes the contacts 23 of the relay K.

If either line conductor becomes open or the potential of the batteryBAT at the remote station fails so that the battery potential relay' A|opens its contacts I3 and I9, the above traced check circuit is openedand the relay H is deenergized. By opening its contacts 2| the relay Hopens the circuit of the start light STL and by opening its contacts 22the locking circuit of the alarm relay K is opened. By closing itscontacts 24 the alarm relay K completes a circuit for the alarm ALthrough the lower normally closed contacts of the start key STK. Withthe alarm key AK in the position shown, an energizing circuit iscompleted for the alarm relay K as soon as the relay H reaches itsdeenergized position. This energizing circuit is cdmpleted from thenegative terminal of the battery BAT through the contacts 26 of therelay H, winding of relay K, contacts 25 of relay K, normally closedcontacts of alarm key AK to the neutral terminal of the battery BAT. Byclosing its contacts 23, the alarm relay K completes a locking circuitfor its winding which is independent of the contacts of the alarm keyAK. Therefore, when the alarm key AK is in the position shown, the alarmAL is operated for only a short time. If, however, the alarm key AK isin its other posiiton so that its contacts are open, the above-tracedenergizing circuit of the alarm relay K is not completed by the closingof the contacts 26 of therelay H and, therefore, the alarm continues tooperate until the dispatcher moves the alarm key AK to the positionshown.

If a short circuit occurs across the line conductors, the increasedcurrent. which flows through the check circuit under this conditioncauses the relay E to open its contacts 2.0 in the circuit of the relayH. Relay H then becomes deenergized and extinguishes the. start lamp STLand efiects the operation of the alarm AL in. the manner abovedescribed.

It will now be assumed that the: supervisory system is in an operativecondition and that the dispatcher desires to operate the apparatus unitAUI to its open position. The dispatcher first operates the select keySKi corresponding to the apparatus unit AU-l so' that the contacts ofthe select key are open. The opening of these contacts disconnects thefirst contact in the bank S from the positive terminal of the batteryBAT. The dispatcher then operates the start key STK so that its uppercontacts are opened and its lower contact is closed. A circuit is thencompleted from the positive terminal of the battery BAT through thelower contacts of the start key STK, winding of start relay P, contacts2'! of relay H, wiper and normal contact of bank T to the neutralterminal n of the battery BAT. Start relay P then operates and byclosing its contacts 28 completes through contacts 29 of the relay H alocking circuit for the coil of relay H. By opening its contacts I 8 therelay P disconnects the line conductor L2 from the neutral terminal n ofthe battery BAT and by closing its contacts 30 connects this lineconductor L-Z to the positive terminal of the battery BAT. By closingits contacts 3|, the relay P short-circuits the windings of the relaysSl and E and the contacts N5 of the emergency reset key ERK so that thenormal contact of the bank S is connected directly to the negativeterminal of the battery BAT. As a result of the operation of the relayP, the voltage impressed across the line conductors Ll and L-2 at thedispatchers' onice is increased and the resistance is decreased so thatthe current which flows through the start relay E at the remote stationis increased sufficiently to cause this relay to close its contact 32and thereby connect the winding ofthe auxiliary starting relay F betweenthe positive terminal and the neutral terminal n of the battery BAT. Byclosing its contacts 33, the relay F completes a locking, circuit forits operating coil through the contacts 34 of the zero position relay Hso that the relay F remains energized until the selector switch A hasleft its zero position. By closing its contacts 35, the relay Fcompletes a shunt circuit around the winding of the relay E, which has arelatively high impedance, so as to increase the current flowing throughthe line conductors to a value sufiicient to cause the armatures of thesynchronizing relays SSH and SSH to move to their left-hand position.

In the dispatchers ofiice the synchronizing relay SSR, by closing itscontacts 36, completes an energizing circuit for the motor magnet m fromthe negative terminal of the battery BAT through the interrupter contactand winding of motor magnet m, wiper and normal contact of bank N andprotective resistor PR| to the positive terminal of the battery BAT. Themotor magnet m then operates in a manner well known in the art to effectthe movement of the selector switch A to its first position. When thewiper associated with the bank N engages its first contact which isconnected to the negative terminal of the battery BAT through protectiveresistor PR2, the circuit of the motor magnet m is not again completedthrough the contacts 36 of the synchronizing relay SSR because bothterminals of the motor magnet are now connected to the negative terminalof the battery BAT. By opening its contacts 5 and closing its contacts36, the synchronizing relay SSR, also reverses the current through thetime delay pick-up relay D so that it maintains its contacts I5 open andits contacts 46 closed for a predetermined time while the selectorswitch A is moving from one position to another. By closing its contacts45, the relay D completes an energizing circuit for the time delay dropout relay C. This relay C is designed, however, so that the contacts 4'!thereof remain closed as long as the selector switch A is operating fromone position to another and for a short time after it stops in anyposition. Therefore the relay C does not open its contacts 41 untilafter the switch A has been stopped for a predetermined time.

In the remote station the synchronizing relay SSR, by closing itscontacts 31, completes a similar energizing circuit for the motor magnetm which effects in a well known manner the movement of the selectorswitch A to its first position. By opening its contacts 6 and closingits contacts 38, the synchronizing relay SSR also reverses the currentthrough the relay C so that the relay C by opening its contacts [2maintains the synchronizing circuit open for a predetermined time afterthe switch A reaches its first position. Relay C, therefore, controlsthe speed at which the selector switches move from one position to thenext.

Since the contacts of the select key SK! have been opened by thedispatcher, no circuit is completed through the wiper and first contactof the bank S when the switch A reaches its first position. A highresistance check circuit, however, is completed which causes the relayA--l to close its contacts 39. This check circuit is from the positiveterminal of the battery BAT, through the contacts 40 of the relay SSR,winding of relay Al, contacts 4| of relay B which complete a shortcircuit around a resistor 42, winding of relay SSR, contacts M of relayF, retardation coil RC|, line conductor LI, contacts l3 of relay A|,retardation coil RC|, winding of relay SSR, contacts I 2 of relay C,wiper and first contact of bank S, winding 2 of relay MOR',

negative terminal of battery BAT, neutral terminal n of battery BAT,retardation coil RC'2, contacts 19 of relay Al, line conductor L-2,retardation coil RC2, contacts l8 of relay P which is deenergized assoon as the switch A leaves its normal position, contacts I! of relay Fto the neutral terminal 11 of battery BAT.

While the current in this check circuit is in the opposite direction tothe last synchronizing current impulse, and therefore is in the properdirection to effect the movement of the armatures of the synchronizingrelays SSR and SSR to their right-hand position, the magnitude of thecurrent is not sufficient to do so. Therefore the switches A and A stopin their first position. If the contacts of the select key SK| had beenclosedwhen the switches reached their first position, the relay Al wouldhave been short-circuitecl by the select key SKI and consequently thecontacts 39 would not have been closed. Also the current through thewindings of the synchronizing relays SSR. and SSR would have beensufiicient and in the proper direction to cause the armatures of therelays SSR and SSH to move to their right-hand position and effect theoperation of the motor magnets m and m to move the switches to theirsecond position. Therefore, it will be seen that the relay A--l closesits contacts 39 only when the selector switches stop in the positioncorresponding to an operated select key.

By closing its contacts 39 the relay A-l completes an energizing circuitfor the relay B. This circuit is from the negative terminal of thebattery BAT through the contacts 39 of relay Al,

contacts H of the relay C, winding of relay B to the neutral terminal 11of the battery BAT. By closing its contacts 48, relay B completes acircuit around the contacts 41 before the relay C operates to open them.Therefore, it will be seen that the relay Al has to close its contacts39 within a predetermined time after the selector switch A stops in anyposition in order to effect the energization of the relay B.

By opening its contacts 4 l, the relay B removes the short circuit fromaround the resistor 42 in the circuit of the relay Al so that the relaywill open its contacts 39 more quickly when its operating coil isdeenergized. By closing its contacts 49 the relay B completes a circuitto light the amber light AMl so as to notify the dispatcher that thedesired apparatus unit AU-l has been properly selected by the selectorswitches. This circuit is from the negative terminal of the battery BATthrough the contacts 49 of the relay B, amber light AM-l, first contactand wiper of bank T to the neutral terminal n of the battery BAT.

As soon as the switch A reaches its first position, a circuit iscompleted from the neutral terminal n of the battery BAT, throughparallel connected operating winding of the relays MIR and P, wiper andfirst contact of bank I, auxiliary contacts 8 on apparatus unit AU-l tothe negative terminal of the battery BAT. The direction of current flowin this circuit is such as to cause the relay MIR to close its contacts53 and the relay P to close its contacts 54. As long as the relay MORmaintains its contacts l5 open the circuit through the contacts 53 ofthe relay MIR is maintained open. By closing its contacts 54, however,the relay P completes a signalling circuit from one terminal of thealternating current source ACl through the contacts 54 of the relay P,contacts 55 of the relay H which is deenergized as soon as the switch Aleaves its normal position, condenser CON"-f, contacts 13 of relay Al,line conductor L-l, contacts 56 of key ERK, then through two parallelcircuits one including the condenser CON| and winding AC-I in series andthe other including condenser CON-2 and winding AC-2 in series and thenthrough line conductor L-Z, contacts H) of relay A'l, condenser CON2 tothe other terminal of the source ACI.

Since the circuit of the winding ACI of the relay MIR is tuned to thefrequency of the source ACI, more current flows through the winding AC-lthan flows through the winding AC-2 when the source AC'-l is connectedacross the line conductors. Therefore, the relay MIR closes its contacts58 in response to the signalling current and completes between thepositive terminal and the neutral terminal 1L of the battery BAT acircuit which includes the contacts 59 of the relay X, wiper and firstcontact of bank I and the operating winding of the indicating relayIR-l. The current in this circuit, however, is in a direction tomaintain the left-hand contacts of the relay IR-l closed. Therefore, thered lamp R| remains lighted.

After the amber light AM-l lights, thereby informing the dispatcher thatthe desired apparatus unit AU-| has been properly selected by theselector switches, and he notes also that the red lamp R-l is stilllighted thereby indicating that the apparatus unit is still closed, thedispatcher operates the operate key OK which completes an energizingcircuit for the operate relay F. This circuit is from the negativeterminal of the battery BAT through the winding of relay F, contacts 50of relay B, contacts of operate key OK, to the neutral terminal 11 ofthe battery BAT.

By closing its contacts the relay F completes a circuit around thecontacts 39 in the locking circuit of relay B so as to maintain therelay B energized as long as the relay F is energized. By opening itscontacts l4 and closing its contacts 60 relay F interrupts theconnection between the line conductor Ll and the positive terminal ofthe battery BAT through the windings of the relays SSR and A-l and thecontacts 40 of relay SSH and connects the line conductor Ll to thenegative terminal of the battery BAT through the wiper and first contactof bank C. By opening its contacts I! and closing its contacts 6| therelay F interrupts the connection between the line conductor L-2 and theneutral terminal 11 of battery BAT through the contacts [8 of relay Pand connects the line conductor L-Z to the positive terminal of thebattery BAT through the wiper and first contact of the bank Cl.Therefore, the result of the operation of relay F is to apply fullpotential of battery BAT across the line conductors in such a manner asto oppose the potential of half of the battery BAT at the remotestation. Therefore, the current through the line conductors is reversedin response to the operation of the relay F.

At the remote station this reverse current which flows through theoperating winding of the relay SSR and the winding 2 of the relay MOR isin a direction to maintain the armature of the relay SSR in itsleft-hand position. Therefore, this reverse current does not change theposition of the armature of the relay SSR. The direction of this reversecurrent, however, is such as to cause the relay MOR to close itscontacts I5 and complete a circuit from the positive terminal of thebattery BAT, through contacts 62 of relay K, winding of relay M,contacts 53 of relay MIR, contacts [5 of relay MOR, contacts 63 of relayB to the neutral terminal n of the battery BAT. By closing its contact64 the relay M completes a shunt circuit around the contacts 53 of therelay MIR so that the relay M remains energized as long as thedispatcher maintains the control key OK in its operated position.

By closing its contacts 65, the relay M completes a circuit from thepositive terminal of the battery BAT through the contacts 65 of relay M,contacts 66 of relay B, wiper and first contact of bank C, winding ofrelay CR| to the neutral terminal 11 of the battery BAT. The current inthe circuit is in a direction to cause the relay CRI to open itsright-hand contacts and close its left-hand contacts thereby completingthrough the auxiliary contact 6'! on the apparatus unit AUl anenergizing circuit for the trip coil TC-I. The energization of the tripcoil TC--l effects the opening of the apparatus unit AU-l.

As soon as the apparatus unit AU-l opens, the current through theoperating coils of the relays MIR and P is reversed by the apparatusunit opening its contacts 8 and closing its contacts 61. As a result ofthis reversal of current the relay MIR opens its contacts 53 and closesits contacts 58 and the relay P opens its contacts 54 and closes itscontacts 69. By opening its contacts 54 the relay P disconnects thesource ACl from across the line conductors and by closing its contacts69, it connects the source AC2 across the line conductors.

Since the circuit of the winding AC-Z of the relays MIR at thedispatchers office is tuned to the frequency of the source AC' the relayMIR operates in response to the connection of the source AC2 across theline conductors to open its contacts 58 and close its contacts it. Therelay MIR thereby reverses the direction of current flow through theindication relay IR| so that it opens its left-hand contacts and closesits right-hand contacts. The opening of the left-hand contacts of therelay IR--l interrupts the circuit of the red lamp Rl so that it isextinguished. By closing its right-hand contacts, the relay IRIcompletes a circuit for the green lamp GR--I directly across thepositive and negative terminals of the battery BAT and a circuit for thewhite lamp Wl through the contacts of the control key CK-I. Thedispatcher can extinguish the White lamp Wl by moving the control keyCK--l so that its position agrees with the new position of the apparatusunit AU-l.

When the dispatcher restores the operate key OK to its normal positionafter effecting the desired operation of the selected apparatus unitAU-l the relay F is deenergized and reconnects the line conductors Lland L--2 to the wiper of bank S and to the neutral terminal 11 of thebattery BAT. In order to insure that the relay B is energized when therelay A-l closes its contacts after the relay F is deenergized, therelay F, when energized, completes through its contacts M an energizingcircuit for the time delay drop-out relay C. Therefore, if the relay A-lcloses its contacts 39 within a predetermined time after the relay F isdeenergized, an energizing circuit is completed for the relay B throughthe contacts 4'! of the relay C.

In response to the deenergization of the relay F at the dispatchersofiice the relay MOR at the remote station opens its contacts l5 andthereby interrupts the circuit of the control relay M which, in turn, byopening its contacts 65 interrupts the circuit of the control relay CR!and the armature of the control relay CR,i, returns to the neutralposition.

After the dispatcher has opened the selected apparatus unit AU-l, he mayeffect the closing thereof by again operating the operate key OK which,in the same manner as above described, causes the relay MOR in theremote station again to close its contacts I5. The closing of thecontacts 15 now, however, effects the energiza tion of the relay Kinstead of the relay M because the contacts 68 instead of the contacts53 of the relay MIR are closed. The circuit of the relay K is from thepositive terminal of the battery BAT through the contacts 13 of therelay M, winding of relay K, contacts 68 of relay MIR, contacts l5 ofrelay MOR', contacts 63 of relay B to the neutral terminal n of thebattery BAT.

By closing its contacts 14 the relay K completes a shunt circuit aroundthe contacts 68 of the relay MIR so that the deenergization of the relayK is not effected by the relay MIR when it changes its position inresponse to the movement of the apparatus unit AU| to its closedposition. By closing its contacts 15, the relay K completes a circuitfrom the negative terminal of the battery BAT through the contacts 15 ofrelay K, contacts 66 of relay B, wiper and first contact of bank C,winding of control relay CRI to the neutral terminal n of the batteryBAT. The current in this circuit is in a direction to cause the controlrelay CR,I to close its right-hand contacts and thereby complete throughthe auxiliary contacts 11 on the apparatus unit AUI an energizingcircuit for the closing coil so that the apparatus unit AU-l is closed.

By opening its auxiliary contacts 61 and closing its auxiliary contacts8 the apparatus unit AU-l reverses the current through the relays MIRand P so that the relay MIR opens its contacts 68 and closes itscontacts 53 and the relay P opens its contacts 69 and closes itscontacts 54. The relay P, therefore, disconnects the signal source AC-2from across the line conductors and connects the source AC-I across theline conductors. Iherefore, at the dispatchers oflice, the relay MIRoperates to open its contacts 10 and close its contacts 58 so that thecurrent through the indication relay IR-I is reversed. The relay IR,Ithen operates to extinguish the green lamp G| and to light the red lampRl and the white lamp W-l. The dispatcher may extinguish the White lampWl by moving the check key CK--l so that its position corresponds to theclosing position of the apparatus unit AUI.

It will be seen, therefore, that after an apparatus unit has beenselected the dispatcher can open and close it as many times as hedesires and that each change in the position of the selected apparatusunit is indicated instantly by the corresponding group of lamps in thedispatchers oflice.

After the dispatcher has effected the desired operation of the selectedapparatus unit AU-I, he may effect the return of the selector switches Aand A to their normal position merely by closing the select key SKI. Theclosing of this select key SKI completes a low resistance shunt circuitaround the relay Al so that suificient current flows through thesynchronizing circuit in the proper direction to effect the movement ofthe armatures of the synchronizing relays SSR and SSR to theirright-hand position and thereby respectively complete enel'gizingcircuits for the motor magnets m and m which move the selector switchesA and A to their second position. The synchronizing circuit is thencompleted through the second contacts of the banks S and S so thatcurrent flows through the circuit in the reverse direction. This reversecurrent causes the armatures of the synchronizing relays SSH and SSR tomove to their left-hand position so that the circuits of the motormagnets m and m are completed to move the selector switches A and A totheir third position. If all of the selector keys are in their normalposition, i

are operated in synchronism until they reach their 24th position wherethe synchronizing circuit is open at the banks S and S. The 23rd and24th contacts of the bank N, however, are connected together so that assoon as the wiper of the bank N engages the 24th contact of the bank,the cir-- cuit of the motor magnet m is again completed and the motormagnet effects the movement of the switch A from its 24th position toits normal position. Similarly, the 23rd and 24th contacts of the bank Nare connected together so that as soon as the wiper of the bank Nengages its 24th contact the circuit of the motor magnet m is againcompleted and the motor magnet effects the movement of the switch A toits normal position.

When both of the switches A and A reach their normal position, theabove-traced check circuit through the relays S-l, E and E is againcompleted and the relay 8-! by closing its contacts l9 completes theabove-described energizing circuit for the relay H which, in turn, byclosing its contacts 2| completes the circuit of the start light STL.Also by opening its contacts 26 and closing its contacts 22, the relay Hmomentarily interrupts the circuit of the alarm relay K which,

by closing its contacts 24, completes a circuit for the alarm AL throughthe lower normal contacts of the start key STK which is now in itsnormal position.

It will now be assumed that while the selector switches A and A are intheir normal position, the current through the closed apparatus unitAU23 in the remote station increases to a value sufficient to cause theoverload relay OL23 to close its contacts 80 so that a circuit iscompleted through the trip coil TC23 and the auxiliary contacts 8| onthe apparatus unit. The energization of the trip coil TC-23 efiects theopening of the apparatus unit All-23. By opening its auxiliary contactsHi the apparatus unit AU23 interrupts the heretofore described lockingcircuit of the indication auxiliary relay IA-23. By closing its contacts82 the relay IA23 completes through the contacts 83 of the zero positionrelay H a circuit for the start relay D. By closing its contacts 8 therelay D completes a circuit for the operating winding of the relay P sothat it closes its contacts and connects through contacts 85 of thestart relay D the source AC--I across the line conductors Ll and L2. Atthe dispatchers ofiice the signal current which is transmitted over theline conductors as a result of the source AC! being connected theretocauses the relay MIR to close its contacts 58 and complete a circuitfrom the positive terminal of the battery BAT through the contacts 58 ofthe relay MIR, contacts 59 of relay X, wiper and normal contact of bankI, upper normal contacts of start key STK, winding of relay P, contacts21 of relay H, wiper and normal contact of bank T to the neutralterminal n of battery BAT. Start relay P then operates in the mannerabove described and effects the starting of the selector switches A andA which continue in operation until they again reach their normalposition. Since the start key STK is in its normal position when theselector switch A leaves its normal position, the alarm AL is operatedin this case in response to the deenergization of the alarm relay K.

As the wipers of the two switches stop momentarily on each contact, anindication of the position of the associate apparatus unit istransmitted in a manner above described to the corresponding indicationrelay in the dispatchers office. Thus, the position of each apparatusunit is checked each time the selector switches are moved to thecorresponding positions. In the case assumed, when the selector switch Areaches its twenty-third position, source AC-2 is connected across theline conductors so that the relay MIR. at the dispatchers ofiice isoperated to cause the relay IR-23 to reverse its position and therebyextinguish the red lamp Iii-23 and light the green lamp G23 and thewhite lamp W23. The lighting of the white lamp W-23 informs thedispatcher which apparatus unit has changed its position and has causedthe selector switches to operate.

At the remote station when the switch A reaches its twenty-thirdposition, a circuit is completed from the neutral terminal 11 of thebattery BAT through the wiper and 23rd contact of the bank T, winding ofrelay IA23, auxiliary contacts 96 on apparatus unit AU23 to the positiveterminal of the battey BAT. Relay IA23 by closing its contacts Hcompletes a shunt circuit around the wiper and 23rd contact of bank T sothat the relay remains energized after the switch A leaves its 23rdposition. Therefore, the starting relay D is not again energized throughthe contacts 82 of the relay IA-23 when the switch A reaches its normalposition.

If at any time the operator desires to check the position of the signallamps at the dispatchers office, he can do so merely by operating thestart key STK. The selector switches A and A will then complete a cycleof operation during which the indicating circuit for each apparatus unitis completed to the corresponding control relay so that it will operateto automatically check the lighting of the corresponding signal lamps.

If at any time the two selector switches get out of synchronism, thedispatcher can restore each switch to its normal position by operatingthe emergency reset key ERK so that its contacts 9| complete a shuntcircuit across the line conductors L--| and L-2. This shunt circuitcompletes a local operating circuit for each synchronizing relay whichoperates independently of the other to effect the return of itsassociate selector switch to its normal position. The circuit of therelay SSR is completed either from the positive or the negative terminalof the battery BAT depending upon the position of the switch A, wiper ofbank S, winding of relay SSR, contacts I4 of relay F, retardation coilRC-l, contacts 9i of emergency reset key ERK, contacts l8 of relay P,contacts I 1 of relay F to the neutral terminal n of battery BAT. Thecircuit of the relay SSR' is from the positive or negative terminal ofthe battery BAT depending upon the position of the switch A, througheither the winding 2 or the winding 3 of relay MOR to the wiper of bankS, thenthrough contacts I2 of relay C, winding of relay SSR, retardationcoil RC-I, contacts l3 of relay A-l, line conductor L-l, contacts 9| ofemergency reset key ERK, retardation coil RC--2, line conductor L2,contacts IQ of relay Al, retardation coil RC2 to the neutral terminal nof the battery BAT. Each synchronizing relay then operates in an obviousmanner to effect the return of its associate selector switch to itsnormal position.

While I have, in accordance with the Patent Statutes, shown anddescribed my invention as applied to a particular system and asembodying various devices diagrammatically indicated, changes andmodifications will be obvious to those skilled in the art and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire tosecure by Letters Patent of the UnitedStates, is:

1. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said stations, synchronously operated selecting means ateach station having a single position individual to each of said units,said means including means for transmitting current impulses throughsaid conductors in series to efiect the synchronous operation of saidselecting means, means for stopping each selecting means in the positionindividual to a unit, means for transmitting through said lineconductors in series a plurality of current impulses while saidselecting means remain in the positions in which they are stopped, meansresponsive to each of said current impulses for effecting an operationof the unit individual to the positions in which the selecting means arestopped, and means for operating the signalling devices individual to aunit in accordance with the positions occupied thereby while saidselecting means are simultaneously in the positions individual to suchunit including means for transmitting through said line conductors inseries signalling current varying in character in accordance with thepositions of such unit.

2. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said station, synchronously operated selecting means ateach station having a single position individualto each of said units,said means including means for transmitting current impulses throughsaid conductors in series to efiect the synchronous operation of saidselecting means, means for stopping each selecting means in a positionindividual to a unit, means for transmitting through said lineconductors in series a plurality of direct current impulses while saidselecting means remain in the positions in which they are stopped, meansresponsive to each direct current impulse for effecting an operation ofthe unit individual to the positions in which the selecting means arestopped, and means for operating the signalling device individual to aunit in accordance with the positions occupied thereby while saidselecting means are simultaneously in the positions individual to suchunit including means for transmitting through said line conductors inseries alternating current varying in character in accordance with thepositions of such unit.

3. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said station, synchronously operated selecting means ateach station having a single position individual to each of said units,said means including means for transmitting current impulses throughsaid conductors in series to efiect the synchronous operation of saidselecting means, means for stopping each selecting means in a positionindividual to a unit, means for transmitting through said lineconductors in series a plurality of impulses of current of one characterwhile said selecting means remain in the positions in which they arestopped, means responsive to each current impulse for effecting anoperation of the unit individual to the positions in which the selectingmeans are stopped, and means for operating the signalling devicesindividual to a unit in accordance with the positions occupied therebywhile said selecting means are simultaneously stopped in the positionsindividual to such unit including means for transmitting through saidline conductors in series signalling current differing in character fromthe operating current impulses and varying in character in accordancewith the positions of the unit.

4. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said stations, synchronously operated selecting means ateach station having a single position individual to each of said units,said means including means for transmitting current impulses of oppositepolarity alternately through said conductors in series to effect thesynchronous operation of said selecting means, means for stopping eachselecting means in a position individual to a unit, means fortransmitting through said line conductors in series a plurality ofdirect current impulses of the same polarity as the last synchronizingimpulse while said selecting means are stopped in the positions thereofindividual to the same unit, means responsive to each direct currentimpulse for effecting an operation of the unit individual to theposition in which the selecting means are stopped, and means foroperating the signalling devices individual to a unit in accordance withthe positions occupied thereby while said selecting means aresimultaneously stopped in the positions thereof individual to such unitincluding means for transmitting through said line conductors in seriesalternating current varying in character in accordance with thepositions of such unit.

5. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said stations, synchronously operated selecting means ateach station having a single position individual to each of said units,said means including means for transmitting current impulses of oppositepolarity alternately through said conductors in series to effect thesynchronous operation of said selecting means, means for stopping eachselecting means in a position individual to a unit, means fortransmitting through said line conductors in series when each selectingmeans has stopped in the position individual to the same unit aplurality of direct current impulses of the same polarity as the lastsynchronizing impulse, means for effecting the operation of the unit inresponse to each of said last mentioned direct current impulses, andmeans for controlling the operation of each of said signalling deviceswhen each selecting means is in the position individual to thecorresponding unit including means for transmitting through saidconductors in series a signal current of one character when thecorresponding unit is in one position and of a different character whenthe corresponding unit is in another position.

6. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling devices at said firststation individual to each apparatus unit, two line conductorsinterconnecting said stations, synchronously operated selecting means ateach station having a single position individual to each of said units,said means including means for transmitting current impulses of oppositepolarity alternately through said conductors in series to effect thesynchronous operation of said selecting means, means for stopping eachselecting means in a position individual to a unit, means fortransmitting through said line conductors in series when each selectingmeans has stopped in the position individual to the same unit aplurality of direct current impulses of the same polarity as the lastsynchronizing impulse, means for effecting the operation of the unit inresponse to each of said last mentioned direct current impulses, andmeans for controlling the operation of each of said signalling deviceswhen each selecting means is in the position individual to thecorresponding unit including means for transmitting through saidconductors in series an alternating current of one frequency when thecorresponding unit is in one position and an alternating current ofanother frequency when the corresponding unit is in another position.

'7. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said station, selecting means for successivelyassociating said apparatus units with said line conductors includingmeans for transmitting current impulses of opposite polarity alternatelythrough said conductors in series and polarity means responsive to saidcurrent impulses for efiecting the operation of said selecting means,means for causing said selecting means to select an apparatus unit foroperation, other polarity responsive means, means including saidselecting means for controlling the connection of said other polarityresponsive means to said line conductors so that the position of saidother polarity responsive means is not reversed in response to thetransmission of said current impulses through said conductors, and meansfor operating a selected apparatus unit including means for transmittingthrough said conductors in series operating current of the properpolarity to efiect a reversal in the position of said other polarityresponsive means and means responsive to the operation of said otherpolarity responsive means for effecting the operation of the selectedapparatus unit.

8. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position and a position individual toeach apparatus unit, a relatively high impedance check circuit includinga source of current and said conductors in series completed by saidselecting means when both are in their normal position, means fordecreasing the impedance of said check circuit, manually controlledmeans at said first station for effecting the operation of saidimpedance decreasing means, means responsive to the increased current insaid check circuit produced by the operation of said impulse decreasingmeans for eifecting the synchronous operation of said selecting means,means responsive to an automatic operation of an apparatus unit at saidsecond station for transmitting a current impulse through saidconductors in series when said selecting means are in their normalposition, and means responsive to said current impulse for efiecting theoperation of said impedance reducing means.

9. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position and a position individual toeach apparatus unit, a relatively high resistance check circuitincluding a source of direct current and said conductors in seriescompleted by said selecting means when both are in their normalposition, means for decreasing the resistance of said check circuit,manually controlled means at said first station for efiecting theoperation of said resistance decreasing means, means responsive to theincreased direct current in said check circuit produced by the operationof said resistance decreasing means for effecting the synchronousoperation of said selecting means, means responsive to an automaticoperation of an apparatus unit for transmitting an alternating currentthrough said conductors in series when said selecting means are in theirnormal position, and means responsive to said alternating current foreffecting the operation of said resistance decreasing means.

10. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position and a position individual toeach apparatus unit, a relatively high impedance check circuit includinga source of current and said conductors in series completed by saidselecting means when both are in their normal position, means fordecreasing the impedance of said check circuit, means responsive to theincreased current in said check circuit produced by the operation ofsaid impedance decreasing means for effecting the synchronous operationof said selecting means, means for transmitting a current impulsethrough said conductors in series while said check circuit is completed,and means responsive to said current impulse for effecting the operationof said impedance reducing means.

11. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position and a position individual toeach an paratus unit, a relatively high resistance check circuitincluding a source of direct current and said conductors in seriescompleted by said selecting means when both are in their normalposition, means for decreasing the resistance of said check current,means responsive to the increased direct current in said check circuitpro duced by the operation of said resistance decreasing means foreffecting the synchronous operation of said selecting means, means fortransmitting an alternating current through said conductors in serieswhile said check circuit is completed, and means responsive to saidalternating current for eiTecting the operation of said resistancedecreasing means.

12. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position and a position individual toeach apparatus unit, a relatively high impedance check circuit includinga source of current and said conductors in series completed by saidselecting means when both are in their normal position, means fordecreasing the impedance of said check circuit, manually controlledmeans at said first station for effecting the operation of saidimpedance decreasing means, means responsive to the increased current insaid check circuit produced by the operation of said impedancedecreasing means for efiecting the synchronous operation of saidselecting means, means responsive to an automatic operation of anapparatus unit at said second station for transmitting a current impulsethrough said conductors in series when said selecting means are in theirnormal position, means responsive to said current impulse for efiectingthe operation of said impedance reducing means, a signal, meansresponsive to a predetermined current in said check circuit forefiecting the operation of said signal, and means controlled by saidmanually controlled means for preventing said current responsive meansfrom eflecting the operation of said signal in response to the increasein current produced in said check circuit by the operation of saidmanually controlled means.

13. In combination, a first station, a second station, apparatus unitsat said second station, two line conductors interconnecting saidstations, selecting means at said second station for associating eachapparatus unit with said line conductors, and means for operating anapparatus unit while it is associated with said conductors includingmeans at said first station for causing a current impulse of apredetermined character to flow through said conductors in series whilethe apparatus unit is being maintained in association with saidconductors by said selecting means, a polarized relay at said secondstation, means including said selecting means for causing a current toflow through the operating winding of said relay in a directioncorresponding to the position of the apparatus unit associated with saidconductors, and means controlled by the position of said relay forcausing said current impulse to effect a certain operation of theapparatus unit associated with said conductor when said relay is in oneposition and a different operation of the apparatus unit when said relayis in another position.

14. In combination, a first station, a second station, apparatus unitsat said second station, two line conductors interconnecting saidstations, se-

lecting means at said second station for associating each apparatus unitwith said line conductors, and means for operating an apparatus unitWhile it is associated with said conductors including means at saidfirst station for causing a current impulse of a predetermined characterto flow through said conductors in series while the apparatus unit isbeing maintained in association with said conductors by said selectingmeans, a control circuit individual to each apparatus unit, meanscontrolled by the position of the apparatus unit being maintained inassociation with said conductors for causing said current impulse toefiect a current having certain characteristics to fiow in thecorresponding control circuit when the apparatus unit is in one positionand a current having other characteristics to flow in the correspondingcontrol circuit when the apparatus unit is in another position, andmeans responsive to said currents for selectively controlling theapparatus unit. I

15. In combination, a first station, a second station, apparatus unitsat said second station, two line conductors interconnecting saidstations, selecting means at said second station for associating eachapparatus unit with said line conductors, and means for operating anapparatus unit while it is associated with said conductors including anapparatus unit while it is associated with said conductors includingmeans at said first station for causing a current impulse of apredetermined character to flow through said conductors in series whilethe apparatus unit is being maintained in association with saidconductors by said selecting means, a control circuit individual to eachapparatus unit, means controlled by the position of the apparatus unitbeing maintained in association with said conductors for causing saidcurrent impulse to effect a direct current to flow in one direction inthe corresponding control circuit when the apparatus unit is in oneposition and in the other direction when the apparatus unit is inanother position, and means in each control circuit responsive to thedirection of current flow therein for selectively controlling theoperation of the corresponding apparatus unit.

16. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnect- V series when said selecting means are simultaneously intheir normal position, means responsive to a predetermined value of saidcurrent for effecting the synchronous operation of said select ingmeans, means for increasing said current to said predetermined value,manually controlled means for effecting the operation of said currentincreasing means, means responsive to the operation of an apparatus unitfor causing current of a different character to flow through saidconductor in series when said selecting means are simultaneously intheir normal position, and means responsive to said last mentionedcurrent for efiecting the operation of said current increasing means.

17. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position, means including manuallycontrolled means at said first station for causing current of apredetermined character to fiow through said conductors in series whensaid selecting means are simultaneously in their normal positions, meansresponsive to said current for efiecting the synchronous operation ofsaid selecting means, means responsive to the operation of an apparatusunit for transmitting current of a different character through saidconductors in series when said selecting means are simultaneously intheir normal positions, and means responsive to said last mentionedcurrent for causing current of said first mentioned predeterminedcharacter to flow through said conductor in series.

18. In a supervisory control system, a first station, a second station,apparatus units at said second station, two line conductorsinterconnecting said stations, selecting means at each station, eachselecting means having a normal position, control means for causingdirect current of a predetermined value to flow through said conductorsin series when said selecting means are simultaneously in their normalpositions, means responsive to said direct current for synchronouslyoperating said selecting means, manual control means at said'firststation for efiecting the operation of said control means, meansresponsive to the operation of an apparatus unit for transmittingalternating current through said conductors in series when saidselecting means are simultaneously in their normal positions, and meansresponsive to said alternating current for effecting the operation ofsaid control means.

19. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling means at said firststation individual to each apparatus unit, selecting means at eachstation, each selecting means having a normal position and a positionindividual to each apparatus unit, control means for causing current ofa predetermined character to flow through said conductors in series whensaid selecting means are simultaneously in their normal position, meansresponsive to said current for effecting the synchronous operation ofsaid selecting means, means controlled by the position of an apparatusunit for transmitting through said conductors in series when both ofsaid selecting means are simultaneously in the positions individualthereto, a signalling current for operating the corresponding signallingmeans in accordance with the position of the apparatus unit, meansresponsive to an operation of an apparatus unit for transmitting saidsignalling current when said selecting means are simultaneously in theirnormal positions, and means responsive to said signal current when saidselecting means are simultaneously in their normal positions foreffecting the operation of said control means.

20. In a supervisory control system, a first station, a second station,apparatus units at said second station, signalling means at said firststation individual to each apparatus unit, selecting means at eachstation, each selecting means having a normal position and a positionindividual to each apparatus unit, control means for causing directcurrent of a predetermined value to fiow through said conductors inseries when said selecting means are simultaneously in their normalpositions, means responsive to said direct current for efifecting thesynchronous operation of said selecting means, means controlled by theposition of an apparatus unit for transmitting through said conductorsin series when said selecting means are simultaneously in the positioncorresponding thereto, an alternating current of position, and meansresponsive to said alternating a predetermined frequency when the unitis in one position and an alternating current of another frequency whenthe unit is in another position, means responsive to an operation of anapparatus unit for causing an alternating current of one of saidfrequencies to be transmitted. through said conductors in series whensaid selecting means are simultaneously in their normal currents foreffecting the operation of said control means when said selecting meansare in their normal position and the operation of said signalling meanswhen said selecting means are in the positions individual to thecorresponding apparatus units.

JAMES H. OLIVER.

